Thread trimming device



June 29, 1965 s. R. FRANKEL.

THREAD TRIMMING DEVICE original Filed April 1o, 195s 6 Sheets-Sheet 1 s.R. FRANKEL THREAD TRIMMING DEVICE original Filed April 1o. 1959 June 29,1965 6 Sheets-Sheet 2 lrivenor: SAMUEL R. FEP'NKER Py-Hfcrnej June 29,1965 THREAD TRIMMING DEVICE Original Filed April l0, 1959 6 Sheets-Sheet3 ,..4 I wgo us SSSL r 's4 IZI "yl-JP; u2 7 8o n IOS MJ Invszr-or;`

Samuel. R-FRP'N HEL BYXMM June 2 9, 1965 s. R. FRANKEL 3,191,562

THREAD TRIMMING DEVICE Original Filed April l0, 1959 6 Sheets-Sheet 4Inward-or;

SPmuEk E. FRANKEL.

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Af-fol'ney June 29, 1965 s. R. FRANKEL 3,191,552

THREAD TRIMMING DEVICE Original Filed April 10, 1959 6 Sheets-Sheet 5lnverli'ov:

51m/wak RFRHNKEL- PH'TOrney June. 29, 196s s. R. FRANKEL Y 3,191,562

THREAD TRIMMING DEVICE Original Filled April 10, 1959 6 Sheets-Sheet 6*isonsllooM-f-ssoMS--l SVHTCH |07 swrrcn log Ms soon soon -I swrrcmoe vlnvenkfor:

SAMUEL RFRHNKEL HHforney United States Patent Office 3,191,562 PatentedJune Z9, 1965 3,191,562 THREAD TRIMMING DEVICE Samuel R. Frankel,siiillington, Pa., assignor to American Safety Table Company, Inc.,Mohnton, Pa., a corporation of Pennsylvania 1 Continuationof'papplication Ser. No. 805,640, Apr. 10, 1959. This application Oct.26, 1962, Ser. No. 233,242 27 Claims. (Cl. 112-252) This inventionrelates to thread trimming devices for sewing machines, and moreparticularly relates to a device for cutting both the needle thread andthe bobbin thread at points very close to the outer surfaces of thematerial being stitchedso that a later final trimming of such threads isnot required, this application being a continuation of my pendingapplication, Serial No. 805,640, filed April 10, 1959, now abandoned. i

In commercial operations utilizing sewing machines for the massproduction of stitched articles, such as in the garment trades, the saleprice of the stitched articles produced is necessarily related to thelabor cost involved in producing such` article. Accordingly, reductionsin the fabrication time of a stitched'article result in the ability tosell such article at a lower price, and labor saving devices aretherefore of great interest to the trade. During the stitching process,it is frequently necessary to sever the needle and bobbin threads Whilethe fabric being stitched is centrally located relative to the needle,that is, when the line of stitching does not terminate at or near theedge `of the fabric. Generally, in such a case, the work must bedisplaced from its position at the end of the line of stitching so thatVsufficient of the needle and the bobbin threads become available forhand cutting, the work then being repositioned to the proper place forstarting the next line of stitching. After the stitching operations haveall been completed it is then necessary to trim olf all of theprojecting thread ends so that the stitched article may present a neatand finished appearance. Such a thread trimming operation is timeconsuming and can contribute materially to the labor costs associatedwith theproduction of a particular stitched article.

In order to :alleviate this thread-trimming proble-m, attempts have beenmade in the past to provide automatic thread cutting means designed toleave a minimum of thread to be trimmed, and which in some cases couldbe ignored. One such thread cutting means has been mounted to the rearof the presser foot to cut the thread by a vertical down stroke of acutting edge. This type of apparatus, of course, could only be used atthe edge of a fabric where the fabric is shifted out from under theneedle and behind the vertical cutting device, in order that the cuttingstroke should cut only the threads and not the underlying fabric aswell; The vertical cutting devices are therefore of limited use, beinghelpful only in those cases where the line of stitching terminates atthe edge ofthe stitched article.

Other mechanical cutting arrangements have been devised which cut thethreads by a cutting stroke in a plane parallel to the surface of thefabric being stitched. Such devices can of course be utilized when thefabric is centrally located under the needle without requiring that thefabric be removed from the sewing machine. However, even cutters of thislatter type leave thread ends of approximately one-eighth of an inch andthe need for subsequent hand trimming of these short ends remains. Myinvention, on the other hand, provides for cutting of the needle andbobbin threads within approximately twohundredths of an inch of thefabric surfaces and consequently completely eliminates the need forsubsequent hand trimming, thus effecting a material saving i-n time.

Briefly, my invention accomplishes thread cutting by apparatus includinga pair of hot wires which rapidly burn through the threads to besevered. One of these wires is associated with the presser foot andserves to sever the needle thread, while the other wire is associatedwith the throat plate above the bobbin and serves to sever the bobbinthread. These hot wires are only energized when so desired by the sewingmachine operator, so that during a normal stitching operation there isno tendency whatever for needle thread and bobbin thread to beprematurely severed.

My invention also includes means for insuring that the sewing machinemay be again immediately utilized after a thread cutting operationwithout having to rethread the needle. The thread cutting operation iscarried out in a particular sequence of steps which follow one anotherautomatically when the thread cutting operation is initiated.Accordingly, it is a primary object of my invention to provide a novelthread cutting apparatus effective when actuated to sever the needlethread and the bobbin thread of a sewing machine very close to the outersurfaces of an article being stitched, to thereby eliminate the need forsubsequent hand trimming of short thread ends. A

It is another object of my invention to provide a novel thread cuttingapparatus for severing the needle thread andbobbin thread of a sewingmachine close to the surfaces of a stitched article by means of operatorcontrolled and selectively energizable hot wires.

Yet another object of my invention is to provide novel thread cuttingapparatus which permits the needle thread and bobbin thread associatedwith the sewing machine to be cut without displacing the article beingstitched from the position it occupies at the end ot the stitchingoperation.

Still another object of my invention is to provide novel thread cuttingapparatus which when actuated, automatically positions the sewingmachine needle in an up position to thereby expose the needle thread forcutting.

Another object of my invention is to provide novel thread cuttingapparatus including means for insuring that the thread cutting operationdoes not unthread the needle of the sewing machine.

The foregoing and other objects of my invention will become apparentfrom a careful reading of the following specification when taken inconjunction with the appended drawings, wherein:

FIGURE 1 is a fragmentary elevational view, partly in section, showingthe Working end of a sewing machine head as seen looking into the frontof the presser foot, and illustrates one view of the thread cutting hotwire system andthe auxiliary means employed to provide thread tensionrelease in order to avoid rethreading of the needle` after a threadcutting operation;

FIGURE 2 is an end elevational View, also partly in section, of thesewing` machine head illustrated in FIGURE l, and illustrates certainorganization details not visible in the latter figure;

FIGURE- 3 is a view of the presser foot as seen when viewed along thelines 3 3 of FIGURE 2;

FIGURE 4 is a sectional view through the presser foot seen in FIGURE 3as viewed along the lines 4 4 of that figure; p

FIGURE 5 is an'underside view of the sewing machine throat, plate asseen when viewed from below along the lines 5-5 of FIGURE l;

FIGURE 6 is an enlarged fragmentary view of that section of the`throatplate of FIGURE 5 which is enclosed in the phantom circle;

FIGURE 7 is a sectional view through the throat plate of FIGURE 5 asseen when viewed along the lines 7--7 of FIGURE 6;

FIGURE 8 is a side sectional view taken through the presser foot as seenwhen viewed along the lines 8 8 of FIGURE 1 and illustrates the needleand bobbin threads in thread cutting position;

FIGURE 9 is aV fragmentary view as seen when looking down from abovealong the lines 9 9 of FIGURE 2 and illustrates the position change fthe auxiliary thread puller arm when energized and deenergized;

FIGURES 10 through 16 illustrate in schematic form theelectrical'circuitry associated with the thread trimming device,successive ones of these iigures illustrating successive phases of thethread cutting operation; I FIGURE l7`is avtiming diagram which shows inpictorial-form thesequence of and actuation duration of the variousswitched circuits embodied in the apparatus of FIGURES 10 through 16.

In these :several figures, like elements are denoted by like referencenumerals.

Turning iirst to an examination of FIGURES 1 and 2 there is seen aconventional sewing machine head having the usual thread lguides 31, and37, a thread eyelet 36, a thread tensioner 32, slack thread regulator33, thread take up lever 34, thread retainer 38, reciprocable needle bar21k and needle 22 and` presser foot assembly 25. The presser footassembly 25 includes a vertically shiftable presser foot shaft 26operated by the presser foot lever 27, the presser foot 29 andsupporting presser foot shank 28 being secured to the presser foot shaft26 by a set screw 24. Immediately underlying the lowered presser foot 29are two plies of fabric 57 and 58 which have been partially stitched,these fabric plies being rmly pressed downward upon the throat plate 51by the presser foot. The needle 22 is shown in its raised position,

Y which is the position occupied when a thread cutting operation is tobe performed.

Underlying the needle hole 52 in the throat plate 51 is seen a bobbin 55from which extends upwardly into Ythe partly stitched fabric plies thebobbin thread 56.

The needle thread 3tlis seen to be drawn from a thread supply andthreaded through'the various thread guides, tensioner, andother'retainers, downward and through the eye of the needle 22. Theforegoing sewing machine elementsA and their organization with respectto one another are seen to be completely conventional. However, certainother elements which appearin FIGURES l and 2, and which have not as yetbeen described repre-sent auxiliary attachments to the sewing machine,and in some cases modification of otherwise standard parts, and it iswith these components that this invention is primarily concerned and towhich attention should be primarily directed. Various aspects of thesecomponents are illustrated in FIGURES 3 through 9 in enlarged form forclarity and ease of understanding. Generally, insof far las themodificationsvwhich appear in FIGURES 1 and 2 are concerned, the newelements are seen to be the auxiliary thread pullers 40 and 60,`and themodiiica tions to standard parts are seen to reside in the inclusion ofthe hot wire elements into the presser foot 29 and throat plate 51. Y Yf Before describing the organizational cooperation Aamongst all of theelements in carrying out the thread trimming operation, it will be mostconductive to a complete understanding of the invention kto firstexamine the modifications made to the presser foot 29 -as best seen inthe showings of FIGURES 3 and 4, and the moditication made to the throatplate 51 as best seen in the showings of FIGURES 5, 6 and 7. Consideringfirst the modified presser foot 29 illustrated in FIGURES 3 and 4,V itis seen that a horizontally transversely extending hole has been drilledthrough the forwardly extending toes 85 of the presser foot 29, and a`wire 80 inserted through the hole and extending outwardly to either sideof the presser foot 29.V The wire 80, which may be made for example ofChromel wire, is bound in a central position within the hole by abonding agent 84, which may i be for example a high temperaturethermosetting epoxy res1n.

The epoxy resin bonding agent 84 serves to insulate the Chromel wire 80from the body of the presser foot 29, and hence prevents the Chromelwire 80 from being electrically short circuited by the presser foot,this latter condition being undesirable for tworreasons. Firstly, shortcircuiting of the Chromel wire 80 by the presser foot 29 wouldeffectively prevent any substantial electrical energizing current frombeing passed through the Chromel wire, with the attendant consequencethat the wire would not be heated and would therefore be renderedinoperative for severing the needleA thread. Secondly, the epoxy resin84 provides a substantial heat barrier between the Chromel wire and thepresser foot 29, without which, the presser foot 29 would act as a heatsink and rapidly conduct away the heat developed in the Chromel wire 80when the latter is electrically energized for thread cutting. In thiscase, also, the Chromel wireV 80 could be rendered inoperative for itspurpose. The characteristics required for the bonding agent S4 aretherefore that it be a good electrical insulating agent, a reasonableheat barrier, and it must not itself be susceptible to break down as aresult of the relatively high temperatures developed in the Chromel wire841, which may be as high as 700 F.

Butt welded or otherwise connected to the ends of the Chromel wire Stiare a pair of copper leads 81, which are in turn each respectivelyconnected to one of the energizing electrical conductors 82 and 83, thelatter being seen in the showings of FIGURES 1 and 2. The manner inwhich the conductors 82 and 83 are energized will be fully described inconnection with the showings of FIGURES 10 through 16 subsequently to bedescribed. The relative position of the Chromel wire 80 in the presserfoot 29 with regard to the sewing machine needle 22 is best illustratedin the showing of FIGURE 8 where it can be seen that the Chromel Wire 80is located substantially to the rear of the needle hole 52 in the throatplate 51, and hence is positioned to the rear of the needle 22, so thatduring normal stitching operations the Chromel wire 80 does notinterfere with the reciprocating motion of the sewing machine needle 22.

Turning now to the showings of FIGURES 5, 6 and 7 illustrating themodiiied throat plate 51, it is seen that a channel has been cut intothe undersurface of the throat plate extending from some convenientpoint on the edge thereof inwardly to encompass the needle hole 52.Within this channel is disposed a second Chromel Wire 7@ which loopsaround the needle hole 52 and eX- tends outwardly toward the edge of thethroat plate 51, being butt welded at its ends to a pair of copper leads'771. The Chromel wire '7d and copper leads '71 are secured within thechannel by a bonding agent 74 which may be Van epoxy resin of the sametype andremployed for the same purposes as the bonding agent 84 alreadydescribed in connection with the showing of FIGURES 3 and 4.

As best seen in the showing of FIGURE 7 the Chromel wire 76 is notycompletely surrounded by the bonding agent 74, but is rather secured tothe throat plate 51 with a free surface portion which may be broughtinto v contact with the bobbin thread 56 in order to sever the latter.The copper leads 71 are each connected in turn to one of a pair ofconductors 72 and 73 which conduct the electrical energizing current tothe Chromel wire during the thread cutting operation. The throat plate51 is provided in the normal manner with feed dog slots 53, as seen inFIGURE 5, but it will be observed that the Chromel wire 70 extendsYtransversely of the righthand most slot. In order that the feed dogswhich ellip` tically oscillate in these -slots 53 to advance the fabricunder the needle 22 should not cut through the Chromel wire 70 andthereby destroy Vthe circuit continuity to the energizing source, thefeed dogwhich oscillates in the right-hand most slot 53 is recesseddownwardly by cutting out several of the teeth thereon to thereby insureclearance between the oscillating feed dog and the Chromel wire 70.

Understanding now that the thread trimming or cutting oper-ation is tobe carried out by heating the Chromel wires 70 and 80 bonded into thethroat plate 51 and presser foot 29 respectively and then laying theneedle thread 3l) and bobbin thread 56 thereagainst in order to burnthrough and sever these threads, it will be appreciated from theshowings of FIGURES 2 and 8 that during some portions of thenormaloperation of the sewing machine th-at needle thread 30 and thebobbin thread 56 do not engage the Chromel wires 70 and 80, and hencesome means must be provided to insure that the bobbin and needle threadsare positively pressed against these wires when it is desired to severthem during a thread trimming operation.

Moreover, if the needle thread 30 were severed while under normaltension maintained during a stitching operation, the needle thread 30would snap back through the eye of the needle 22 and hence require thatthe needle be rethreaded before stitching could be resumed. It is thespecific function of the auxiliary thread puller 40 mounted to thesewing machine head near the thread tensioner 32 to provide a certainamount of slack in the needle thread 3@ so that the needle 22 is notunthreaded when a thread trimming operation is carried out. The functionof the auxiliary thread puller 60 mounted below the throat plate 51 andadjacent the bobbin 55 is to displace the bobbing thread 56 from itscentral position in the needle hole 52 of the throat plate and to shiftthis bobbin thread laterally and generally rearwardly into positiveengagement with the Chromel wire 70 which trims the needle hole 52.

Examining now FIGURES l and 2 for details of the auxiliary` threadpullers `40 and '66, it is seen that the auxiliary thread puller 4t)includes a loop-ended arm 45 secured to a sleeve 43 by a machine Screw46, and that the sleeve 43 is secured to the shaft 42 of a rotarysolenoid 41 by a machine screw 44. The rotary solenoid 41 is affixed toa bracket 47 which is in turn secured to the sewing machine head by apair of screws 59. The rotary solenoid 41, when energized via theconductors 49 and 50 causes the solenoid shaft 42 to rotate and carrythe arm 45 outward away from the sewing machine head 2G. The needlethread 30, which is passed through the loop on the end of the arm 45when the machine is first threaded, is carried outward with the arm 45.Since the needle thread 30 cannot be back pulled out of the stitchedfabric plies 57 and 58, the pull exerted on the needle thread 30 by therotation of the arm 45 causes thread to be pulled from the thread supplythrough the thread tensioner 32. Hence, when the arm 45 returns to itsposition as illustrated in FIGURE 2 upon deenergization of the rotarysolenoid 41, a predetermined amount of slack results in the needlethread 30 which relieves the tension therein sufficiently to preventunthreading of the needle 22 upon severance of the needle thread 30 bythe Chromel wire 80.

The auxiliary thread puller 6! associated with the bobbin thread 56 issimilar in construction and operation to the auxiliary thread puller 40and is so positioned relative to the bobbin thread 56 and needle hole 52of the throat plate 51 that rotation of the arm 61 pulls a predeterminedamount of thread outwardly from the bobbin 55 and causes the bobbinthread 56 to be laid over firmly against the exposed surface of theChromel wire 70 in the throat plate 51. FIGURE 9 illustrates exemplarypositions of the arm 45` of the auxiliary thread puller 40 whendeenergized and whcnenergized, the solid line construction illustratingthe` normal or deenergized state of the rotary solenoid 41 and thebroken line showing the displaced position of the arm 45 when the rotarysolenoid 41 is energized. The identical action takes place, of

course, with regard to the arm 61 of the rotary solenoid incorporatedinto the auxiliary thread puller 60, energization of this solenoid beingby means of the conductors 62 and 63. 1

The one remaining point to be considered before turning to anexamination of FIGURES 10 through 17 for an understanding of theoperational sequence which takes place when a thread cutting operationis initiated, is the means by which the needle thread 30 which normallylies in advance of the Chromel wire in the presser foot 29 is shiftedrearwardly into trimming position against the Chromel wire. Since inorder to cut the needle thread 30, it is necessary that the needle 22 beraised to expose the thread, advantage is taken of the fact that thefabric being stitched is advanced through the sewing machine a distanceequal to one-half stitch when the needle 22 is shifted from its down toits up position.

The half step fabric advance is accomplished by the motion of the feeddogs which grip the under side of the fabric .through the feed dog slots53 in the throat plate 51. One of the feed dogs 54 is shown inrepresentational form in the showing of FIGURE 8 where it is likewiseseen that the half stitch fabric advance displaces the needle thread 3()rearwardly a suiiicient dist-ance to bring it into engagement with theChromel wire S0, and wherein 4likewise it may be seen that the bobbinthread 56 has been similarly shifted rearwardly by the arm 61 of theauxiliary thread puller 6) so that it firmly engages the exposed surfaceof the Chromel wire 70 embedded in the underside f-o the throat plate51.

In summary, the general sequence of events will be as follows. First,the sewing machine must be stopped with the needle 22 in raised positionto expose the needle thread 30 and advance the fabric one-half stitchrearward to properly position the needle thread 30 and bobbin thread 56.Then the thread trimming operation proper is initiated which includesthe energization of the auxiliary thread pullers 40 and 60 torespectively provide a slack action in the needle thread 30 and apositive engagement action of the bobbin thread 56 with the Chromel wire70. Finally, the Chromel wires 70 and 80 are energized sufficiently toburn through the needle thread 30 and bobbin thread 56 to complete thethread trimming operation. Understanding now the general manner in whichthe thread cutting operation is to be carried out according to theinvention, attention should be directed to the showings of FIGURES l0through 17 where conttrol apparatus for selectively energizing therotary solenoids and the thread cutting Chromel wires in a particulartimed sequence is illustrated in detail.

Examining irst FIGURE 10, there is seen a transformer 96 `having aprimary winding 91 connected to a source of alternating current by theconductors 113 and 114, and having three independent secondary windings92, 93 and 94. The secondary winding 92 is connected .to a pair ofcrystal rectiiiers 95 in a full-wave rectifying circuit, the rectifiedvoltage therefrom being applied to the solenoid coil 64 of the auxiliarythread puller 6i) by the conductors 63 and 62 through the switch 108-when the latter is closed. Similarly, the rectified output of thefull-wave circuit including the secondary winding 93 and the crystalrectifiers 96 is applied to the solenoid coil 48 -of the auxiliarythread puller 40 via the conductors 49 and 50 through t e switch 107when the latter is closed.

One end of the secondary winding 94 is connectedvia a conductor 111 tothe movable contacts 66 4and 68 of a pair of rheostats 65 and 67respectively, while the other end of the winding 94 is connected to thejunction of the conductors 72 and 82 associated with the Chromel wires70 and 30 via the conductor 110 and the switch 109 when the latter isclosed. Theconductors 73 and 83 associated respectively with the Chromelwires 70 and 80 connect to one end of the rheostats 65 and 67respectively, thus forming a continuous electrical circuit when theswitch 169 is in its closed position. The rheostats 65 and 67 are seento be respectively series connected Vwith the Chromel wires '70 and 80and are therefore effective to control the magnitude of thecurrentthrough lthese wires between limits established by the maximumand minimum settings of the rheostat movable contacts'd and 68.

In general the rheostats 65 and 67 would be available to the sewingmachine openator as setable controls. The machine operator is therebyenabled to set these rheostats to provide the necessary amount ofheating current to sever diierent kinds Vof threads, as for example, aiirst setting for cotton threads and a different setting for nylonthreads. The Various setting of the rheostats once determined may bemarked on a suitable escutcheon plate positioned behind the control knobfor each of the rheolstats movable contacts so that rapid resetabilityto desired contact positions in easily achieved.

The switches 107, 198 and 109 are shown in their normally open conditionand are only closed in response to a closing pressure exerted thereon bythe cams 103, 1&4 Aand 165 respectively of the timer 10@ when cammot-ion is initiated and maintained by the energization of the winding1ll1`of the timer motor. The remaining cam 1112 yof the timer i)actuates the holding switch 1% to maintain the timing motor winding1tl1energized during the thread cutting cycle of operation, and toenergize and stop the timer at the completion of the operation. Thetimer motor winding 1111 is energized from the same source ofalternating current which energizes the primary Winding of. thetransformer 90, such winding energization being switch controlled.

The current flow path through the ywinding 161 may be traced from oneterminal of the alternating current source to the lower end of thewinding 1111 via the conductors 113 and 112, through the Winding 101 andfrom the top of the winding to the pole of the switch 106 via theconductor 119. the switch 1116'is returned to the other side ofthealternating current source via the conductor'115, the latter beingconnected'to the lower contact of the switch 122. The right-handcontactof the switch 1115 connects via the conductor-116m the'pole ofthe .switch 122 -through the normally` open switch 123. Thus, toenergize the timer motor, the pole of'the switch 122 is transferred fromits normally open upper contact to the lower contact, which Y thencloses 4the electrical circuit from the source of alternating currentthrough the Winding 10.1 ofthe timer motor. Ganged to the pole of theswitch .122 is the pole of a second switch 121 which is shown in anormally open condition, the pole of the switch 4121 being connected toone conductor 117 of -an external circuit (not shown), and the lowercontact of the switch 121 being also connected to the same externalcircuit via the conductor 118. The

The normally open left-hand contact of two switches 121 and 122aretherefore ganged together l for simultaneous actuat-ion and mayoptionally be com. bined into one double-pole single-throw switch. VThe`switches 121 and-122 a-re operator actuated and in fact are theswitches which initiate the thread cutting operation. i

Recall-ing now from the earlier description that the sewing machineneedle 22 must be in its raised position when a thread cutting operationis initiated, it is clear that it wouldfbe highly desirable to relievethe operator yfrom the `burden of turning lthe balance wheel by hand toraise the needlewhen he wishes to trim the needle and bobbin threads.The switch 121 is provided to accomplish the automatic needle raisingsimultaneously with the initiation ofl the thread -cutting operationprovided that the sewing machine is already equipped with an automaticneedle positioning mechanism such as is described in my applicationentitled Automatic Needle Positioning Mechanism, assigned'to t-he sameassignee as the instant application, nowv matured as United StatesPatent No. 2,961,591, dated November 22, 1960.` In this regard, theswitch 121 when actuated by. theV operator, performs the sam'efunctionas the knee-lift switch 1119 in FIGURE l0 d of my copending applicationby completing a circuit between the conductors 111i and 1-11 as showntherein,

Returning now to FIGURE l0 of the instant application, the normally openswitch ,123 shown therein is provided to insure that the timing motorwinding 1111 may not be energized unless the sewing machine has beenstopped. The switch 123 may be incorporated into the sewing machinetreadle mechanism in such a way that it is opened when the treadle isdepressed to operate the sewing machine and closes when the treadle isreleased and the sewing machine is therefore broughtto a stop. Theinclusion of the switch 1123 is of course optional and may 4be dispensedwith if desired. In FIGURES 11 through 16 which follow, the switch123would normally be closed and it is therefore not included in theseshowings.

The timing diagram of FIGURE l7 illustrates the closure conditions forthe switches 106, 107, 108 and 1119 relative to one another during thethread cutting operation, and the duration of the conditions pictured ineach of the sequence diagrams of FGURES 1l through 16 are correlatedinto the timing diagram of FIGURE 17. In the following description ofFGURES ll through 16 reference should be simultaneously made to FIGURE.17.

Turning now to the conditions` as illustrated in the showing of FIGUREl1, it will be assumed that the sewing machine has come to a stop andthat the operator ha-s actuated the ganged switches .121 and 122. Theswitches 121 and 122 are preferably of the momentary-make type and donot require to be held closed by the Voperator or by any locking typedevice. The actuation of the switches i121 and 122 causes the sewingmachine needle to rise by actuation of the automatic needle positioningmechanism previously mentioned, `and closes a circuit from a source `ofalternating current `through theY winding 1111 of the timer motor. Thecurrent flow circuit through the time-r motor winding 1111 is shown in-heavy line in FIGURE ll and may be traced from the source ofalternating current down through the conductor 115 and 4over to therighthand contact of the switch 1126 via the now closed switch A122 andconductor 116. :From the switch 1616 the current flows via conductor 119to the top of the timer motor winding 1111, down through the winding andback to the yother terminal of ythe source of alternating current viathe conductor 112.

Energization of the timer motor causes the motor shaft to rotatecarrying with it the cams 1112, 1623, 1114 and 165. None of the switches1116 through 109 are actuated for approximately titty milliseconds afterinitiation yof the thread cutting operation as may be seen from thetiming diagram `of FIGURE 17. The fifty millisecond interval insuresthat ample time is provided to allow the sewing machine needle to riseto its upper position. At the end yof this time, the cam 1012 hasrotated sufficiently to cause the pole of the switch 166 to transferfrom its right-hand contact to its left-hand contact, .as will be seenin FIG- URE l2, and thereby establish the current flow path y throughthe timer motor winding 101-to the conductor 115 by bypassing theconductor 116 and switch 122.

When the momentary-make swi-tch `122 now opens (as also seen in FIGUREl2) the energization ottimer motor winding 1111 is not interrupted butis maintained througr the holding circuit established by the transfer ofthe pole of thev switch 166. The timer mo-tor continues to run :androtate the shaft to which the cams 162 through 1115 are aiiixed forapproximately two seconds after the pole `of the switch 122 transfers,and during the first one-hundred and titty milliseconds of this timenone ofthe switches y167, 1113 or 1119 are closed. Consequently, therotary solenoid coils 418 and e4 remain deenergized and no energizingcurrent is delivered to the Chrome] wires 711 and Sil.

FIGURE l2 illustrates the `conditions after the lapse of approximatelyone-hundred and fifty milliseconds from the initiation of the threadcuttingv operation by closure of Vthe switches 121and 122. At this timecams 103 and 194 respectively close the switches 167 and 1118V toenergize the rotary solenoid coils 48 and 64. The auxiliary threadpullers 40 and 60 are therefore energized and the arms 45 and 61 aredisplaced in the manner and for the purposes previously described. Thecam 105 has, however, not rotated into such position as will close theswitch 109 and hence the Chromel wires 70 and 80 remain deenergized. Theconditions of FIGURE 12 are maintained for approximately one-hundred andfifty milliseconds, at the end of which time the cam 103 of the timer100 causes the switch 107 to open and thus deenergize the solenoid coil48 of the auxiliary thread puller 40 associated with the needle thread.

The conditions obtaining for the next fifty milliseconds are seen in theshowing of FIGURE 13 where it is observed that the solenoid coil 64 ofthe auxiliary thread puller 60 remains energized through switch 108 andthereby holds the bobbin thread 56 over against the Chromel wire 70 inthe throat plate 51. The bobbin thread 56 is thus prepared for severancewhen the Chromel wire 70 is subsequently energized, and the needlethread 30 has experienced a substantial reduction in tension to preventunthreading of the needle 22 upon the subsequent energization of theChromel wire 80.

At the end of the fifty millisecond time interval during which theconditions of FIGURE 13 hold, the cam 105 of the timer 100 closes theswitch 109 as seen in FIGURE 14 and thereby energizes the Chromel wires70 and 80 from the transformer secondary winding 94 via the conductors110, 111 and the rheostats 65 and 67. Cam 104 of the timer 100, ofcourse, continues to hold the switch 108 in its closed condition tothereby maintain the solenoid coil 64 of the auxiliary thread puller 60in its energized condition and keep the bobbin thread 56 firmly overagainst the Chromel wire 70. The conditions of FIG- URE 14 continue forapproximately fiftymilliseconds, at the end of which time cam 105 of thetimer 100 allows the switch 109 to open and thus deenergize the Chromelwires 70 and 80, fifty milliseconds having been found to be a sufficientlength of time to cause severance of varying kinds of needle and bobbinthreads.

Upon the opening of the switch 109, the conditions as illustrated inFIGURE 14 are altered to thoseas seen in the showing of FIGURE 15wherein it is seen that the timer continues to run by virtue of theenergization of the winding 101 of the timer motor through the holdingcircuit of switch 106, and that the solenoid coil 64 of the auxiliaryvthread puller 60 continues in its energized state. The conditions ofFIGURE 15 are maintained for approximately one-hundred milliseconds, atthe end of which time the cam 104 of the timer 100 allows the switch108Y to open and thus deenergize the solenoid coil 64 of the auxiliarythread puller 60 and establish the conditions as now seen to hold in theshowing of FIGURE 16.

The entire operation up to 'this point occupies a time interval ofapproximately ve-hundred milliseconds, as may be seen in the showing ofthe timing diagram of FIG- URE 17, and the timing motor continues to runfor an additional fifteen-hundred milliseconds during which time onlythe switch 106 remains actuated by its associated cam 102. At the end ofthis total two second time interval commencing with the initiation ofthe thread cutting operation, the came 102 Aof the timer 100 allows the'switch 106 to transfer its pole from the left-hand contact over to thelight-hand contact and thus break the holding circuit for the motorwinding 101. The timer motor therefore stops and the conditionsportrayed inthe showing of FIGURE are again established. l i 1 It may befound desirable in some instances to establish a safety interlockarrangement whereby the transfer of the pole of switch 106 to establishthe holding current circuit for the timer motor Winding causes thesewing machine to be rendered inoperable until the thread cuttingoperation has been terminated. Although, not shown, such an interlock isvery easily incorporated into the thread cutting apparatus by forexample .providing the switch` 106 with a second pole and associatednormally open contact. This second pole end associated normally opencontact may be connected in series with a source of energizing currentand a solenoid coil the solenoid when energized actuating a plunger orother latching mechanism to lock the sewing machine treadle and therebyprevent operation of the sewing machine stitching mechanism during thethread trimming operation. At the end of the thread trimming operationwhen the switch 106 is restored to its normal position, the second polethereof would of course break open from engagement with its associatedcontact and thereby deenergize the solenoid coil to unlock the treadle.

Having now described my invention in connection with the particularembodiment illustrated in the appended drawings, many modifications andvariations of my invention will naturally suggest themselves to thosepersons normally skilled in the art without departing from the essentialspirit or scope of my invention, and accordingly it is intended to claimthe same broadly as Well as specifically as indicated by the appendedclaims.

What is claimed as new and useful is:

1. In combination with a sewing machine, a thread trimming device forsevering the needle thread of the sewing machine comprising, anelectrically energizable heat generating element, shiftable sewingmachine presser foot means for supporting said element in operativeposition in closely spaced relationship to the upper surface of anarticle being stitched, energizing means effective when actuated tocouple said element to a source of electrical energization, controlmeans coupled to said energizing means and under the control of thesewing machine operator for selectively actuating said energizing means,and means for shifting the needle thread against said heatgenerating'element when said shiftable presser foot is in a firstselected position, whereby, when -said shiftable presser foot is in saidfirst selected position, when the needle thread is in engagement withsaid heat generating element, and when said control means is actuated,said element is energized and rendered effective to burn through theneedle thread.

2. The thread trimming device according to claim 1 wherein said sewingmachine includes a reciprocating needle having an eye therein forreceiving the needle thread and further includes needle thread tensionreducing means actuatable by the sewing machine operator and effectivewhen actuated to reduce the needle thread tension prior to severance ofthe needle thread by said heat generating element, whereby said needlethread when severed does not snap back through the needle eye andunthread the needle.

3. The thread trimming device according to claim 1 wherein said presserfoot means includes a presser foot having laterally spaced toe portionsand said electrically energizable heat generating element is aresistance wire having a portion thereof extending freely within thespace between the toe portions of the presser foot and proximate to theaxis of reciprocation of the sewing machine needle.

4. A thread trimming device for severing the needle thread of a sewingmachine comprising in combination, a shiftable sewing machine presserfoot having laterally spaced toe portions including an electricallyenergizable heat generating resistance wire disposed within atransversely extending hole passing through the toe portions of thepresser foot, said resistance wire being physically fixed within saidpresser foot hole and electrically insulated from said presser foot by abonding agent having the ability to withstand without breakdown themaximum temperature developed in said resistance wire, first meanseffective when actuated to couple said resistance wire to a source ofelectrical energization, second means coupled to said first means andunder the control of the sewing machine operator for selectivelyactuating said first means, and third means for shifting the needlethread against said resistance wire during at least a portion of thenormal repetitive reciprocation cycle of the needle when said presserfoot is seated down against the upper surface of is down, when theneedle thread is in engagement with said resistance wire, and when saidsecond means is actuated by the sewing machine operator, said resistancewire is energized and rendered effective to burn through the needlethread.

5. A thread trimming device for severing the needle thread of a sewingmachine, comprising in combination,

within said presser foot so that the sewing machine needle passesVV infrontV thereof during vertical reciprocation of the needle during astitching operation, first means effective when actuated to couple -saidresistance wire to a source of electrical energization, second meanscoupled to said iirst meansand under the control of the sewing machineoperator for selectively actuating said first means, and third means,for shifting the needle thread against said resistance wire during atleast a portion of the normal repetitive reciprocation cycle of theneedle when said presser foot is seated down against the upper surfaceof an article being stitched, whereby, when said presser foot is down,when the needle thread is in engagement with said resistance wire, andwhen said second means lis actuated by the sewing machine operator, saidresistance wire isl energized and rendered effective to burn through theneedle thread.

6. A thread trimming device for -severing the needle .thread of a sewingmachine having a needle thread tensioningdevice and a reciprocatingneedle with an eye therethrough for receiving the needle threadcomprising, an electrically energizable heat generating element, rstpresser foot means for supporting said element in closely spacedrelationship to the upper surface of an article being stitched,secondmeans eiective when actuated to couple said element to a source ofelectrical energization, third means coupled to said second means andunder the control ofV the'sewing machine operator for selectivelyactuating said second means, fourth means for shifting the needlethreadagainst said heat generatingelement during at leastva portion of thenormal repetitive reciprocation cycle of the needle when said shiftablesupporting means is in a irst selected position, and needle threadtension reducing means actuatable by the sewing machine operator andeffective when actuated to reduce the needle thread tension priorytoseverance of the needle thread by said heat generating element, saidneedle thread tension reducing means'comprising a loop-ended swingablearm with the needleV thread passing through the loop in said arm, saidvarm loop being located betweenk the needle and said sewing machineneedle thread tensioning device along the course -of the needle thread,saidtension reducing means further including electrically energizablefifth means coupledto said swingable arm and effective when energized toswing said arm and draw thread-from the needle thread supply throughsaid sewing machine needle thread tensioning device so that the needlethread tension is reduced below that normally obtaining, and sixth meanseffective when actuated for coupling 4said fifth means to a source ofenergization, whereby, whensaid shiftable supporting means is inV saidirst selected position, when the needle thread is in engagement withsaid heat generating element, and when said third'and sixth'rneans'areactuated, said element is energized and rendered effective to burnthrough the needle thread and said needle thread when'severed does notsnap back through theV needle eye and unthread the needle. Y

7. A thread trimmingdevice for severing the needle thread of a sewingmachine having a reciprocating needle with an eye therethroughforreceiving a needle thread, comprising, an electrically energizableheat generating element, presser foot means for supporting saidelementin closely spaced relationship to the upper surface of an article-beingstitched, lirst actuating-means elective when operated to couple saidelement to a source of electrical energization, means for shifting theneedle thread against said heat generating element when said presserfoot means is down, and needle thread tension reducing means actuatableby the sewing machine operator and elective when actuated to reduce theneedle thread tension prior to severance of the needle thread by saidheat generating element, said needle thread tension reducing meansincluding a swingable arm and electrically energizable means coupled tosaid swingable arm and effective when energized to swing said arm andreduce the needle thread tension below that normally obtaining, secondactuating means eiective when operated for coupling said electricallyenergizable thread tension reducing means to a source of energization,and control means under the control ofvthe operator for operating saidfirst and second actuating means whereby, when said presser foot meansis down, when the needle thread is in engagement with said heatgenerating element and when said control means is operated, said elementis energized and rendered effective to burn through the needle threadand said needle thread when severed Vdoes not snap back through theneedleeye and unthread the needle.

8. The thread trimming device according to claim 6 whereinv said thirdmeans is also coupled to said sixth means and controls theV actuationthereof, said third means actuating said sixth and second means in apredetermined sequence and for predetermined time intervals.

9. The thread trimming device according to claim 8 wherein said secondand sixth means each include a switch which when closed completesanelectrical circuit between the source of energization and said heatgenerating element and electrically energizable fth means respectively,`and wherein said third means includes a plurality of motor driven.rotatable cam elements, a tirst one of said cam elements being efectiveduring a part of its rotation cycle to close the second means switch,and a different one of said'cam elements being. etective during part ofits rotation cycle to close the sixth means switch, each cam elementbeingy soshaped relative to the other and so positioned relative to itsassociated switch that said switches are closed. in the saidpredetermined sequence as said cams rotate. f

10. The thread trimming device according to claim 7 wherein said rst andsecond actuating means each include a switch which when closed completesan electrical ,circuit between the source of energization and said heatgenerating element and electrically energizable thread tension reducingmeans respectively, and wherein said control means includes a pluralityof motor driven rotatable cam elements, a first one of said cam elementsbeing effective duringV a part of its rotation cycle to close theiirst'actuating means switch, and a different one of said cam elementsbeing eifective during part of its rotation cycle to close the secondactuating means switch, each cam element being so shaped relative to thelother and so positioned relative to its associated switch that saidswitches are closed in a predetermined sequence and for predeterminedtime intervals as said cams rotate.

11. A thread trimming device for severing the bobbin thread of asewingmachine, comprising in combination, an electrically energizable heatgenerating resistance wire, a sewing machine throat plate having aneedle hole eX- tending therethrough and carrying said resistance wirein closelyspaced relationship to the under surface of an article beingstitched with the resistance wire disposed in 'substantially encirclingrelationship to the needle hole inf the throat plate, rst meanseffective when actuated to vcouple said element to a source ofelectrical energization, asecond means effective when energized forshifting the bobbin thread intoY positive engagement with saidheat'generating element,'third means effective when actuated forcoupling said second means to a source of energization, and `fourthmeans under the control of the sewing machine operator for selectivelyactuating said first and third means, whereby, when said fourth means isoperated said heat generating element is energized and the bobbin threadis shifted into positive engagement therewtih.

12. The thread trimming device according to claim 11 wherein saidresistance wire is physically fixed to said throat plate by a bondingagent electrically insulating said wire from said throat plate, being agood heat barrier, and having the ability to withstand without breakdownthe maximum temperature developed in said resistance wire. i

13. A thread trimming device for severing the bobbin thread of a sewingmachine having a throat plate with a needle hole extending therethroughcomprising, an electrically energizable heat generating element, firstmeans for supporting said element in closely spaced relationship to theunder surface of an article being stitched, second means effective whenactuated to couple said element to a source of electrical energization,third means effective when energized for shifting the bobbin thread intopositive engagement with said heat generating element, fourth meanseffective when actuated-for coupling said third means toa source ofenergization, and fifth means under the control of the sewing machineoperator for selectively actuating said second and fourth means,whereby, when said fifth means is operated said heat generating elementis energized and the bobbin thread is shifted into posi` tive engagementtherewith, said third means comprising a loop-ended swingable arm withthe bobbin thread passing through the loop in said arm, said arm loopbeing located along the course of the bobbin thread between the bobbinand the throat plate needle hole, said third means further includingelectrically energizable sixth means coupled to said swingable arm andeffective when energized to swing said arm and shift the bobbin threadinto positive engagement with said heat generating element.`

`14. The thread trimming device according to claim 13 wherein saidsecond and fourth means each include a switch which when closedcompletes an electrical circuit between the source of energization andsaid heat generating element and electrically energizable sixth meansrespectively, and wherein said fifth means includes a plurality ofrotatable cam elements, a first one of said cam elements being effectiveduring a part of its rotation cycle to close the second means switch,and a different one of said cam elementsbeing effective during part ofits rotation cycle to close the fourth means switch, each cam ele-` mentbeing so shaped relative to the other and so positioned relative to itsassociatedA switch that said switches are closed in a predeterminedsequence and for predetermined time intervals as said cams rotate.

15. A thread trimming device for severing the bobbin thread of a sewingmachine, comprising in combination, an electrically energizable heatgenerating resistance wire, a sewing machine throat plate having aneedle hole eX- tending therethrough and carrying said resistance wirein closely spaced relationship to the under surface of an article beingstitched with the resistance wire disposed adjacent to the needle holein the throat plate, first actuating means effective when actuated tocouplesaid element to a source of electrical energization, meanseffective when energized for shifting the bobbin thread into positiveengagement with said heat generating element, second actuating meanseffective when actuated for coupling said thread shifting means to asource of energization, and control means under the control of thesewing machine operator for selectively actuating said first and secondmeans, whereby, when said control means is operated said heat generatingelement is energized and the bobbin thread is shifted into positiveengagement therewith, said first and second actuating'means eachincluding a switch which when closed completes` an electrical circuitbetween the source of energization and said lheat generating element andelectrically Venergizable thread shifting means respectively, and saidcontrol means including a plurality of rotatable cam elements, a firstone.

' and a different one of said cam elements being effective during partof its rotation cycle to close the second actuating means switch, eachcam element being so shaped relative to the other and so positionedrelative to its associated switch that said switches are closed in apredetermined sequence and for predetermined time intervals as said camsrotate.k

16. The thread trimming device according to claim 14 wherein said fifthmeans further includes an electrically energizable motor effective whenenergized to rotate the aforesaid plurality of rotatable cam elements,said cam elements being coupled to the motor shaft for rotationtherewith, an operator actuatable switch effective when actuated tostart said motor by connecting the motor energizing winding to a sourceof electrical energization, and a switch closable by one of saidplurality of rotatable cams for establishing a holding current circuitbetween said motor winding and source of electrical energization in thetime interval during which said operator actuatable switch is actuated,the cam which closes ythe holding current circuit switch being so shapedthat said switch is held closed` for a time interval substantially equalto the duration of the thread trimming operation and then causes saidswitch to open to deenergize said motor and terminate the threadtrimming operation.

, 17. The thread trimming device according to claim 15 wherein saidcontrol means further includes an electrically energizable motoreffective when energized to rotate the aforesaid plurality of rotatablecam elements, said cam elements being coupled to the motor shaft forrotation therewith, an operator actuatable switch effective whenactuated to start said motor by connecting the motor energizing windingto a source of electrical energization, and

a switch closable by one of said plurality of rotatable cams forestablishing a holding current circuit between said motor winding andsource of electrical energization in the time interval during which saidoperator actuatable switch is actuated, the cam which closes the holdingcurrent circuit switch being so shaped that said switch is held closedfor a time interval substantially equal to the duration of the threadtrimming operation and then causes said switch to open to deenergizesaid motor and terminate the thread trimming operation.

18. The thread trimming device according to claim 16 further includingmeans in series with said operator actuatable switch for rendering thelatter inoperative to start said motor when the sewing machine drivemechanism is operating.

19. The thread trimming device according to claim 16 comprising furthermeans including a switch ganged to said holding current circuit switchand operable therewith for rendering the sewing machine inoperableduring the thread trimming operation by actuating a device which locksthe sewing machine treadle to thereby prevent operation of the same bythe sewing machine operator.

20. A thread trimming device for severing the needle thread of a sewingmachine comprising, an electrically energizable heat generating element,first shiftable means for supporting said element in closely spacedrelationship to the upper surface of an arti fe being stitched, secondmeans effective when actuated to couple said element to a source ofelectrical energization, third means coupled to said second means andunder the control of the sewing machine operator for selectivelyactuating said second means, and fourth means for shifting the needlethread against said heat generating element during at least a portion ofthe normal repetitive reciprocation cycle of the needle when saidshiftable supporting means is in a first selected position, said fourthmeans comprising sewing machine feed dogs which advance the fabric beingstitched for a distance equal to one half stitch as the sewing machineneedle moves from its down to its up position so that the needle threadextending upward from the fabric is shifted rearward against theelectrically energizableiheat generatingelement, whereby, when saidshiftable supporting means is in said first selected position, when theneedle thread is in engagement with said heat generating element, andwhen said third means is actuated, said element is energized andrendered effective to burn through the needle thread.

2l. A thread trimming device for severing the needle thread of a sewingmachine, lcomprising in combination, an electrically energizable Vheatgenerating element, means for supporting said heat generating element inclosely spaced relationship to the upper surface of an article beingstitched, means for'shifting the needle thread against said heatgenerating Ielement when the latter is disposed as aforesaid closelyabove the article being stitched during at least a portion of the'normalrepetitive reciprocation cycle of the needle, and means selectivelyoperable under the control of the sewing machine operator effective whenoperated to couple said heat generating element to a source ofelectrical energization, whereby, when the needle thread is inengagement with said heat generating. element operation of said lastVnamed means renders said heat generating element effective'to burn'through said needle thread, said means for shifting the needle threadagainst said heat generating' elementpcomprising sewing machine feeddogs which advance the fabric being stitched for a distance equal to onehalf stitch as the sewingV machine needle moves from its down to its upposition so'that the needle thread extending upward from the articlebeing stitched isshifted rearward against the electrically energizableheat generating element.

22. A thread trimming device for` severing the needle thread of a sewingmachine having a needle thread tensioning device and a reciprocatingneedle with an eye therethrough forreceiving the needle thread,comprising in combination, rvan electrically energizable heat generatingelement, means for supporting said heat generating element in closelyspaced relationship to the upper surface of an article being stitched,means for shifting the needle thread against said heat generatingelement when the latter is disposed as aforesaid closely above thearticle being stitched during at least a portion of the normalrepetitive reciprocation cycle of the needle, needle thread tensionreducing means comprising a loop-ended swingable arm located betweenlthe needle and said sewing machine needle thread tensioning devicealongthe course of the needlel thread with the needle thread passing throughthe loop in said arm, electrically energizable means coupled to saidswingable arm and effective when energized to swing said arm and drawthread from the needle thread supply through said sewing machine needlethread tensioning device, and means selectively operable under thecontrol of the sewing machine operator effective when operated to couplesaid heat generating element and said energizable needle thread armswinging means to a source of electrical energization, whereby, when thevneedle thread is in engagement with said heat generating elementoper-ation of said last named means is effective to reduce the needlethread tension prior to severance of the needle threadand renderV saidheat generating element effective to burn through' said needle thread sothat said needle thread when severed does not snap back through theneedle eye and unthread the needle. Y .23. The apparatuses set forth inclaim 1 further including,V a thread trimmingdevice for severing thebobbin thread of the sewing machine, comprising in combination, anelectrically energizable heat generating resistance wire, a sewingmachine throat plate having a needle hole eX- tending therethrough andcarrying said resistancewire in closely spaced relationship to the undersurface of an article being stitched with the resistance wire disposedadjacent Vto the needle hole in the throat plate, electricallyenergizable means effective when energized for shifting l@ the .bobbinthreadV into positive engagement withsaid resistance wire, and means-selectively operable under the control of the sewing machine operatoreffective when operated to couple said resistance wire and said bobbinthread shifting means to a source'of electrical energization, whereby,upon operation of said last named means a loop-ended'swingable armdisposed so that the bobbinv thread passes through the loop in said arm,said arm loop being located along the course of the bobbin threadbetween the bobbin and the throat plate needle hole, electricallyenergizable means coupled to said swingable arm and effective whenenergized to swing saidarm Iand shift the vbobbin thread into positiveengagement with said heat generating element, and means selectivelyoperable under the control ofthe sewing machine operator effective whenoperated to couple said heat generating element and saidl arm swingingmeans to a source of electrical energization, whereby, upon operation ofsaid last named kmeans said heat generating element is renderedeffective to burn through the bobbin thread and the bobbin thread isshiftedV into positive engagement therewith.

25. The apparatus as set forth in claim 23 in which the sewing machineincludes `a throat plate with a needle hole therethrough and a bobbinbeneath the throat plate,

wherein, said bobbin thread shifting means comprises ka shiftable memberlocated between the bobbin and the throat plate needle hole and disposedso that the bobbin thread passes therethrough.

26. The thread trimming device `according to claim 15 wherein saidcontrol 4means further includes an electrically energizable motoreffective when energized to rotate the aforesaid plurality :of rotatablecam elements, said cam Y elements being coupled to the motor shaft forrotation therewith, an operator actuatable switch effective whenactuated to start said motor by connecting the motor energizing windingto ya source of electrical energization, and

switch closable by one of said plurality of rotatable cams forestablishing a holding current circuit between said motor winding andsource of electrical energization in the time interval during which saidoperator actuatable switch is actuated, the cam which closes the holdingcurrent circuit switch being so shaped that said switch is held closedfor a time interval substantially equal to theduration of the threadtrimming operation and then causes said switch to open to deenergizesaid motor and terminate the thread trimming operation, and meansinseries with said operator actuatable switch for rendering'the latterinoperative to start said motor when the sewing machine drive mechanismis operating.

27. The thread trimming device according to claim 15 wherein saidcontrol means further includes an electricallyy energizable motoreffective when energized to rotate the* aforesaid'plurality ofrotatable' cam elements, said cam* elements being coupled to the motorshaft for rotation therewith, an operator actuatable switch effectivewhen lactuated to start said motor by connecting the motor energizingWinding to a source of electrical energization, and a switch closable byone of said plurality of rotatable cams for establishing a holdingcurrent Acircuit between said motor winding and source of'electricalenergization in the time interval duringwhich said operator lactuatableswitch Vis actuated, the cam which closes the holding current circuitswitch being so shaped that Said switch is heldclosed for a timeinterval substantially equal to the duration of the thread trimmingoperation and then causes said switch to open to deenergize said motorand terminate the thread trimming operation, a switch ganged to saidholding current circuit switch and operable therewith for rendering thesewing machine inoperable during the thread trimming operation byactuating a device which locks the sewing machine treadle to therebyprevent operation of the same by the sewing machine operator.

References Cited bythe Examiner UNITED STATES PATENTS 2,3 46,594 4/ 44McCann 112-252 1 8 4/46 Stahl et al. 112-252 X 5 5 5 Artzt 112-252 9/ 58 Ketterer 112-252 8/ 62 Bi11i 66--145 X FOREIGN PATENTS 1/ 19 Germany.2/ 19 Germany.

10 JORDAN FRANKLIN, Primary Examiner.

DAVID I. WILLIAMOWSKY, Examiner.

1. IN COMBINATION WITH A SEWING MACHINE, A THREAD TRIMMING DEVICE FORSEVERING THE NEEDLE THREAD OF THE SEWING MACHINE COMPRISING, ANELECTRICALLY ENERGIZABLE HEAT GENERATING ELEMENT, SHIFTABLE SEWINGMACHINE PRESSER FOOT MEANS FOR SUPPORTING SAID ELEMENT IN OPERATIVEPOSITION IN CLOSELY SPACED RELATIONSHIP TO THE UPPER SURFACE OF ANARTICLE BEING STITCHED, ENERGIZING MEANS EFFECTIVE WHEN ACTUATED TOCOUPLE SAID ELEMENT TO A SOURCE OF ELECTRICAL ENERGIZATION, CONTROLMEANS COUPLED TO SAID ENERGIZING MEANS AND UNDER THE CONTROL OF THESEWING MACHINE OPERATOR FOR SELECTIVELY ACTUATING SAID ENERGIZING MEANS,AND MEANS FOR SHIFTING THE NEEDLE THREAD AGAINST SAID HEAT GENERATINGELEMENT WHEN SAID SHIFTABLE PRESSER FOOT IS IN A FIRST SELECTEDPOSITION, WHEREBY, WHEN SAID SHIFTABLE PRESSER FOOT IS IN SAID FIRSTSELECTED POSITION, WHEN THE NEEDLE THREAD IS IN ENGAGEMENT WITH SAIDHEAT GENERATING ELEMENT, AND WHEN SAID CONTROL MEANS IS ACTUATED, SAIDELEMENT IS ENERGIZED AND RENDERED EFFECTIVE TO BURN THROUGH THE NEEDLETHREAD.